Influence of alkaline activator solution ratio on the properties of biomass fly ashbased alkali-activated materials

Abstract

This study investigated the use of untreated high carbon biomass fly ash (BFA) and less alkaline Na2CO3 as an activator to produce alkali-activated materials (AAM). This paper examined how the Na2CO3/Na2SiO3 (SC/SS) ratio of alkaline activator solution (AAS) affected the setting time, structure development, and physical-mechanical characteristics of the BFA-based AAM pastes cured at ambient temperature. The initial and final setting times of AAM pastes decrease, respectively, with an increase in the SC/SS ratio. The AAM sample with the smallest SC/SS ratio possesses the lowest density and UPV value, and the highest water absorption. After 7 days of curing, the compressive strength of AAM samples decreased as the SC/SS ratio rose. Nevertheless, the compressive strength of AAM samples increased with increasing SC/SS ratio after 28 days of curing. The SEM studies supported the results for density, water absorption, and UPV, showing that as the SC/SS ratio grows, the structure of the samples becomes denser and more homogenous, consistent with the higher compressive strength of the samples.